package com.site.util;
/**
 * RSA 公钥加密算法是1977年由Ron Rivest、Adi Shamirh和LenAdleman在（美国麻省理工学院）开发的。
 * RSA取名来自开发他们三者的名字。RSA是目前最有影响力的公钥加密算法，它能够抵抗到目前为止已知的所有密码
 * 攻击，已被ISO推荐为公钥数据加密标准。RSA算法基于一个十分简单的数论事实：将两个大素数相乘十分容易，但
 * 那时想要对其乘积进行因式分解却极其困难，因此可以将乘积公开作为加密密钥。 
 */
import java.security.InvalidKeyException;
import java.security.KeyPair;
import java.security.KeyPairGenerator;
import java.security.NoSuchAlgorithmException;
import java.security.interfaces.RSAPrivateKey;
import java.security.interfaces.RSAPublicKey;

import javax.crypto.BadPaddingException;
import javax.crypto.Cipher;
import javax.crypto.IllegalBlockSizeException;
import javax.crypto.NoSuchPaddingException;

import com.site.common.constants.DateSecurityUtil;


public class EncrypRSA {

	protected String encryptRES(RSAPublicKey publicKey, byte[] srcBytes)
			throws NoSuchAlgorithmException, NoSuchPaddingException,
			InvalidKeyException, IllegalBlockSizeException, BadPaddingException {
		if (publicKey != null) {
			// Cipher负责完成加密或解密工作，基于RSA
			Cipher cipher = Cipher.getInstance("RSA");
			// 根据公钥，对Cipher对象进行初始化
			cipher.init(Cipher.ENCRYPT_MODE, publicKey);
			byte[] resultBytes = cipher.doFinal(srcBytes);
			return DateSecurityUtil.parseByte2HexStr(resultBytes);
		}
		return null;
	}

	/**
	 * 解密
	 * 
	 * @param privateKey
	 * @param srcBytes
	 * @throws NoSuchAlgorithmException
	 * @throws NoSuchPaddingException
	 * @throws InvalidKeyException
	 * @throws IllegalBlockSizeException
	 * @throws BadPaddingException
	 */
	protected byte[] decryptRES(RSAPrivateKey privateKey, String buff)
			throws NoSuchAlgorithmException, NoSuchPaddingException,
			InvalidKeyException, IllegalBlockSizeException, BadPaddingException {
		byte[] buffByte = DateSecurityUtil.parseHexStr2Byte(buff);
		if (privateKey != null) {
			// Cipher负责完成加密或解密工作，基于RSA
			Cipher cipher = Cipher.getInstance("RSA");
			// 根据公钥，对Cipher对象进行初始化
			cipher.init(Cipher.DECRYPT_MODE, privateKey);
			byte[] resultBytes = cipher.doFinal(buffByte);
			return resultBytes;
		}
		return null;
	}

	/**
	 * @param args
	 * @throws NoSuchAlgorithmException
	 * @throws BadPaddingException
	 * @throws IllegalBlockSizeException
	 * @throws NoSuchPaddingException
	 * @throws InvalidKeyException
	 */
	public static void main(String[] args) throws NoSuchAlgorithmException,
			InvalidKeyException, NoSuchPaddingException,
			IllegalBlockSizeException, BadPaddingException {
		EncrypRSA rsa = new EncrypRSA();
		String msg = "123abc";
		// KeyPairGenerator类用于生成公钥和私钥对，基于RSA算法生成对象
		KeyPairGenerator keyPairGen = KeyPairGenerator.getInstance("RSA");
		// 初始化密钥对生成器，密钥大小为1024位
		keyPairGen.initialize(1024);
		// 生成一个密钥对，保存在keyPair中
		KeyPair keyPair = keyPairGen.generateKeyPair();
		// 得到私钥
		RSAPrivateKey privateKey = (RSAPrivateKey) keyPair.getPrivate();
		// 得到公钥
		RSAPublicKey publicKey = (RSAPublicKey) keyPair.getPublic();

		// 用公钥加密
		byte[] srcBytes = msg.getBytes();
		String resultBytes = rsa.encryptRES(publicKey, srcBytes);

		// 用私钥解密
		byte[] decBytes = rsa.decryptRES(privateKey, resultBytes);

		System.out.println("明文是:" + msg);
		System.out.println("加密后是:" + new String(resultBytes));
		System.out.println("解密后是:" + new String(decBytes));
	}

}